azat

#include <sys/mman.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <assert.h>
#include <string.h>

void* mmap_hint()
{

azat

SELECT *
FROM system.distribution_queue
FORMAT Vertical

Query id: bb17b27d-c681-4826-8eb6-607a960414f3

Row 1:
──────
database:              default
table:                 dist

azat

/// https://github.com/aosp-mirror/platform_bionic/blob/master/benchmarks/atomic_benchmark.cpp

/*
 * Copyright (C) 2017 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0

azat

select version();
-- ┌─version()───┐
-- │ 20.3.15.133 │
-- └─────────────┘

create table ranges_data engine=Memory() as select number key, number value from numbers(100);
create dictionary default.ranges_dict (key UInt64, value UInt64 default 1) primary key key source(clickhouse(host '127.0.0.1' port 9000 table 'ranges_data' db 'default' user 'default' password '')) lifetime(0) layout(cache(size_in_cells 100));
create table dist as system.one engine=Distributed('test_cluster_two_shards', system, one, dictGetUInt64('default.ranges_dict', 'value', toUInt64(dummy)));

SELECT *

azat

#!/usr/bin/env bash

# XXX: cannot use expect since we need two clients
# XXX: requires bash 4.4+

function assert()
{
    if ! "$@"; then
        echo "'$*' failed" >&2
        exit 1

azat

// gist for showing that rand() with global lock is slower ~60x times
// (came to this for librdkafa random partitioning with producer per group, and eventually program has ~1200 threads)
//
// $ g++ -DRAND -o rand -O3 -pthread rand.cpp
// $ g++ -DRAND_R -o rand_r -O3 -pthread rand.cpp
//
// $ time ./rand
//
// real    0m2.336s
// user    0m2.685s

azat

// Gist to check possible issues with MADV_DONTNEED
// For example it does not supported by qemu user
// There is a patch for this [1], but it hasn't been applied.
//   [1]: https://lists.gnu.org/archive/html/qemu-devel/2018-08/msg05422.html

#include <sys/mman.h>
#include <stdio.h>
#include <stddef.h>
#include <assert.h>
#include <string.h>

azat

2020-09-22 00:48:35 01502_jemalloc_percpu_arena:                                            [ FAIL ] 7.43 sec. - return code 66
2020-09-22 00:48:35 ==================
2020-09-22 00:48:35 WARNING: ThreadSanitizer: data race (pid=384)
2020-09-22 00:48:35   Write of size 8 at 0x7b1000008ff8 by main thread (mutexes: write M1432):
2020-09-22 00:48:35     #0 operator delete(void*, unsigned long) <null> (clickhouse+0x8085f1e)
2020-09-22 00:48:35     #1 Poco::Logger::~Logger() /build/obj-x86_64-linux-gnu/../contrib/poco/Foundation/src/Logger.cpp:39:1 (clickhouse+0x14dc78ce)
2020-09-22 00:48:35     #2 non-virtual thunk to Poco::Logger::~Logger() /build/obj-x86_64-linux-gnu/../contrib/poco/Foundation/src/Logger.cpp (clickhouse+0x14dc78ce)
2020-09-22 00:48:35     #3 Poco::RefCountedObject::release() const /build/obj-x86_64-linux-gnu/../contrib/poco/Foundation/include/Poco/RefCountedObject.h:82:24 (clickhouse+0x14dcb797)
2020-09-22 00:48:35     #4 Poco::Logger::shutdown() /build/obj-x86_64-linux-gnu/../contrib/poco/Found

azat

/**
 * Reproducer for percpu_arena jemalloc issue [1].
 * Requires debug jemalloc (w/o NDEBUG to include assert()s)
 *
 *   [1]: https://github.com/jemalloc/jemalloc/pull/1676
 *
 * $ gcc -g3 -o /tmp/sched /tmp/sched.c
 * $ MALLOC_CONF=percpu_arena:percpu LD_PRELOAD=jemalloc/build/lib/libjemalloc.so taskset --cpu-list 3 /tmp/sched
 * <jemalloc>: ../src/jemalloc.c:321: Failed assertion: "ind <= narenas_total_get()"
 * Aborted (core dumped)

azat

function array_exist()
{
    local needle="$1"
    shift

    local i
    for i; do
        [ "$needle" = "$i" ] && return 0 || continue
    done
    return 1